As a pattern of a semiconductor device becomes finer, recently, a technique of observing and evaluating a speck minute portion of the semiconductor device with the use of a TEM (Transmission Electron Microscope) has increasingly become important. In order to prepare a laminated sample serving as such a specific minute portion, an FIB (Focused Ion Beam) apparatus is used typically. However, the FIB causes a problem of damage due to a focused ion beam as a required thickness of a sample becomes small. Therefore, a method for removing such damage has been required.
As a solution of the situation described above, for example, there has been proposed a method for irradiating an ion beam containing, as an ionic species, a chemical element which is low in chemical activity, such as argon, at a low acceleration voltage of not more than several kilovolts (refer to Patent Document 1).
In order to accurately prepare a TEM sample containing a specific minute portion of a semiconductor, on the other hand, there has also been proposed a system having an FIB and an SEM (Scanning Electron Microscope) coupled to each other, as disclosed in Patent Document 2, for example. In this system, a laminated sample to be prepared is subjected to a micromachining process with the use of the FIB while being carefully observed with the use of the SEM such that the sample includes a specific site to be observed.
Moreover, there has also been proposed a system using combined three beams from an FIB, an SEM and a gas ion beam in order to achieve the merits described above (Non-Patent Document 1). In the composite charged-particle beam system having the three charged-particle beam apparatuses integrated with one another, an arrangement of the respective charged particle beam apparatuses and a relation between the arrangement of the respective charged-particle beam apparatuses and a degree of freedom of a sample stage becomes a very important factor in order to design such a system that a user can conduct work efficiently while making use of characteristics of the respective charged-particle beam apparatuses. In the following, the reasons therefor are described.
Firstly, an FIB apparatus, an SEM and a gas ion beam apparatus are typically required to be arranged near a sample in order to advantageously converge beams from those apparatuses. However, as beam apparatuses to be integrated with one another increase in number, it is difficult to arrange all the beam apparatuses under preferable conditions. Secondly, a sample such as a semiconductor wafer is subjected to observation and fabrication while being tilted; therefore, a space for tilting the sample must be ensured in a sample chamber, resulting in further restriction of a space in which charged-particle beam apparatuses can be arranged freely. Thirdly, with regard to a sample stage, it is difficult to sufficiently improve a degree of freedom of the stage for all charged-particle beams from the viewpoint of space, accuracy, rigidity and cost. Consequently, usability of a composite charged-particle beam system largely depends on a relation between the degree of freedom of the stage and the arrangement of the charged-particle beam apparatuses.
As described above, the arrangement of the respective charged-particle beam apparatuses and the relation between the arrangement of the respective charged-particle beam apparatuses and the degree of freedom of the sample stage becomes a very important factor in order to design such a system that the user can conduct the work efficiently while making use of the characteristics of the respective charged-particle beam apparatuses. However, no mention has been made of this fact in the conventional disclosure.
Patent Document 1: Japanese Unexamined Patent Publication No. 10-221227
Patent Document 2: Japanese Patent No. 3,041,403
Non-Patent Document 1: Toshiaki Fujii, “FIB Apparatus Capable of Suppressing Damage upon Preparation of Samples” (SM13000-series), Electronic Materials and Parts, (June, 2004), pp. 36-38.